A system and method for measuring the flow field on the surface of large ships in wind tunnel tests

Abstract

The present invention discloses a system and method for measuring the flow field on the surface of a large ship in a wind tunnel test. The system installs a Hall element on the front of a stepper motor fixing frame, and a small magnet is fixed on the motor turntable. When the ship's pitch and roll system is in operation and the small magnet is closest to the Hall element, the Hall element obtains an electrical signal and transmits it to a synchronizer as a trigger signal for the particle image velocimetry system to shoot. The synchronizer controls a laser transmitter to emit a laser beam, which is irradiated on a distant reflector. The direction of the laser beam is deflected, and a surface laser is obtained through a circular glass rod to illuminate the flow field section to be studied. This special optical path gets rid of the size limitation of the laser generator and the space limitation brought by the wind tunnel structure, while avoiding the influence of the laser transmitter on the wind field. The measurement system and method of the present invention can accurately locate and phase-lock the cross-section of the ship model in a certain posture during the motion cycle to obtain the flow field characteristics of the ship surface.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind tunnel tests, and in particular relates to a system and method for measuring the flow field on the surface of a large moving ship in a wind tunnel test. Background Art

[0002] my country has a vast territorial waters and a correspondingly long coastline, with a large north-south span and difficult coastal defense forces to put in place. Therefore, the development of aircraft carriers and amphibious assault ships is of great significance. Amphibious assault ships are mainly responsible for large-scale transportation, armed attacks, armed landings and other tasks. Among them, the carrier-based aircraft of amphibious assault ships, which use the deck of the mother ship as a take-off and landing platform, serve as pioneers and mobile forces and play a key role in the execution of tasks. However, due to the small space on the ship deck and the complex sea conditions, the ship will experience a complex shaking process, and its unique take-off and landing environment will severely test the maneuverability of the carrier-based aircraft; the complex movement of the ship, the changes in the incoming flow, and the complex buildings on the deck will make the deck flow field complex and dangerous, which will endanger the safety of the carrier-based aircraft during take-off and landing, so it is crucial to carry out research on the deck flow field.

[0003] Although the research on ship flow field has become more and more extensive in recent years, due to the particularity of ship flow field research, most of the research remains in the field of numerical calculation, and there are relatively few studies on the flow field changes of ships when they roll and pitch at sea. At present, in the traditional ship model flow field measurement test, static small ship models are used, which cannot realize the dynamic ship deck flow field measurement of large ships. There are many problems in the dynamic ship deck flow field measurement of large ships, such as: due to the large size of the wind tunnel test section and the ship model, the particle image velocimetry equipment cannot be built into the wind tunnel, and the external laser control and generation device cannot be correctly irradiated due to the limitation of the optical guide arm; when the large ship model moves, the ship attitude angle and the particle image velocimetry shooting cannot be triggered synchronously, resulting in the shooting data not corresponding to the ideal situation; when the wind tunnel test time is tight and the experimental task is heavy, the number of experimental vehicles should be reduced to complete the experiment and achieve the experimental purpose of flow field measurement; how to shoot the special attitude angle of the large dynamic ship model. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a system and method for measuring the flow field on the deck of a large moving ship in a wind tunnel test. The method overcomes the temporal and spatial limitations of optical path limitations, synchronous triggering, attitude positioning, and multiple measurements of one wind in wind tunnel experiments, and realizes the measurement of the flow field on the deck of a large ship in a wind tunnel test.

[0005] The measurement system of the present invention is mainly used in conjunction with a ship attitude dynamic simulation system for wind tunnel testing disclosed in the Chinese invention patent application with application number 2019110749419.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical solutions:

[0007] A system for measuring the flow field on the deck of a large ship in a wind tunnel test, comprising a ship model, a motion control subsystem and a particle image velocimetry component. The motion control subsystem comprises a motor component, the motor component comprises a stepper motor, a U-groove bearing and a motor turntable, the motor turntable has a central hole for mounting on the rotating shaft of the stepper motor, and a slot is provided at a certain distance from the central hole for mounting the U-groove bearing. The particle image velocimetry component comprises a Hall element, a small magnet, a laser emitter, a reflector, a cylindrical glass rod, a CCD camera, a synchronizer and a particle image processing system. The small magnets are distributed on the same circumference inside the motor turntable, the Hall element is fixed on the stepper motor fixing frame, and the Hall element is directly opposite to the circumference where the small magnets are distributed. The CCD camera and the laser emitter are both connected to the synchronizer, the reflector is located on the light path emitted by the laser emitter, and the reflector reflects the laser to the direction of the ship model. The cylindrical glass rod is located at the tail of the ship model, and the cylindrical glass rod scatters the laser beam reflected by the reflector into a surface laser; the CCD camera is used to photograph the deck of the ship model.

[0008] Furthermore, the small magnets are arranged according to the phases required for shooting, and when the motor turntable rotates, the small magnets face the Hall element within a certain period of time.

[0009] Furthermore, the Hall element is a unipolar Hall element for outputting an electrical signal.

[0010] A method for measuring using the above-mentioned measuring system comprises the following steps:

[0011] After connecting the pull rope, adjust the ship model to a neutral position, that is, ensure that the roll angle of the ship model is zero; adjust the U-slot bearing at the motor turntable to the farthest distance from the ship model, that is, ensure that the slot hole of the motor turntable and the center hole of the motor turntable are on the same vertical line; tighten the pull rope, and finally ensure that the pull ropes on both sides are in a taut stress state, while the ship model and the motor turntable are in a neutral position at the same time.

[0012] When the stepper motor rotates clockwise, the rope on one side of the ship model is pulled up, and one side of the ship model begins to rise; after the motor turntable rotates 90° from the neutral position, the model rises to the maximum roll angle; when the stepper motor rotates to 180°, the model returns to the neutral position with a roll angle of 0°; the stepper motor continues to rotate from 180°, at this time the rope on the other side of the ship model is pulled up, and the other side of the model begins to rise, and reaches the maximum upward angle when the stepper motor turntable rotates to 270°, and when the turntable rotates back to the neutral position (360°), the model returns to the neutral state with a roll angle of 0°; the above is a motion cycle of the wind tunnel test ship attitude dynamic simulation system simulating roll motion;

[0013] In the process of simulating the ship's posture, every time the motor turntable reaches the corresponding position, the small magnet approaches the Hall element, and the Hall element outputs a low-level signal to the synchronizer, which transmits it to the CCD camera and laser transmitter, and the CCD camera takes a picture.

[0014] The present invention discloses a system and method for measuring the surface flow field of large ships in wind tunnel tests, focusing on the solution of ship motion, phase-locked shooting and optical path construction in wind tunnel periodic motion ship surface flow field test tests. A Hall element is installed on the front of the stepper motor fixing frame, and a small magnet is fixed on the motor turntable. When the ship's roll system is running and the small magnet is closest to the Hall element, the Hall element obtains an electrical signal and transmits it to the synchronizer as a trigger signal for the particle image velocimetry system to shoot. The synchronizer controls the laser transmitter to emit a laser beam, which shines on a distant reflector. The direction of the laser beam is deflected, and a surface laser is obtained through a circular glass rod to illuminate the flow field section to be studied. This special optical path gets rid of the size limitation of the laser transmitter and the space limitation brought by the wind tunnel structure.

[0015] The measurement system and method of the present invention can realize the precise roll and pitch motion of a large ship model in a wind tunnel, and can accurately locate and phase-lock the cross-section of the ship in a certain posture during the motion cycle to obtain the flow field characteristics on the ship surface; this system obtains the flow field shooting in the required posture by changing the delay time in the particle image velocimetry software to filter the Hall element transmission signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of a part of the motion control mechanism of the present invention;

[0017] Figure 2 yes Figure 1 Schematic diagram of the motor assembly structure;

[0018] Figure 3 It is a schematic diagram of a system for measuring the flow field on the surface of a large ship in a wind tunnel test according to the present invention;

[0019] Figure 4 It is a schematic diagram of the specific structure of the dynamic ship model deck flow field test;

[0020] Figure 5 It is a schematic diagram of the wind tunnel test structure of the present invention;

[0021] Figure 6 It is an effect diagram of the relationship between the pitch angle of the ship model and the upwash vortex volume in the wind tunnel test of the present invention.

[0022] Among them: 1. Optical plate, 2. Small triangular fixing block, 3. Turnbuckle, 4. Pulley, 5. Support rod, 6. Large triangular fixing block, 7. Motor assembly, 71. Stepper motor, 72. U-slot bearing, 73. Motor turntable, 74. Hall element, 75. Small magnet, 8. Synchronizer, 9. Particle image processing system, 10. Laser transmitter, 11. CCD camera, 12. Reflector, 13. Cylindrical glass rod, 14. Ship model. DETAILED DESCRIPTION

[0023] In conjunction with the accompanying drawings, a system and method for measuring the flow field on the deck of a large ship in a wind tunnel test proposed by the present invention is described in detail below; in the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part", "bottom" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction; "first", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limitations on the present invention; the specific dimensions used in this example are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

[0024] like Figure 1 , 3 As shown in FIG. 5 , the present invention discloses a system for measuring the flow field on the surface of a large ship in a wind tunnel test, including a ship model 14, a motion control subsystem and a particle image velocimetry component. Figure 1 As shown, the motion control subsystem includes a motor assembly 7, such as Figure 2 As shown, the motor assembly 7 includes a stepper motor 71, a U-groove bearing 72 and a motor turntable 73. The motor turntable 73 has a central hole for mounting on the rotating shaft of the stepper motor 71, and a slot is provided at a certain distance from the central hole for mounting the U-groove bearing 72. The stepper motor is a high-precision, high-torque stepper motor with a single output shaft and an encoder, which can adjust parameters such as speed and acceleration, and is placed above the wind tunnel when in use.

[0025] like Figure 3As shown, the particle image velocimetry assembly includes a Hall element 74 , a small magnet 75 , a laser emitter 10 , a reflector 12 , a cylindrical glass rod 13 , a CCD camera 11 , a synchronizer 8 , and a particle image processing system 9 .

[0026] The small magnet 75 is a cylindrical small magnet with a diameter of 3 mm. The small magnets 75 are distributed on the same circumference inside the motor turntable 73. The Hall element 74 is fixed on the fixed frame of the stepper motor 71, and the Hall element 74 is directly opposite to the circumference where the small magnets 75 are distributed. The Hall element 74 is a unipolar Hall element, which is used to output an electrical signal. The small magnets 75 are arranged according to the phases to be photographed. When the motor turntable 73 rotates, the small magnets 75 are directly opposite to the Hall element 74 for a certain period of time.

[0027] The CCD camera 11 and the laser emitter 10 are connected to the synchronizer 8. The reflector 12 is located on the optical path emitted by the laser emitter 10. The reflector 12 reflects the laser to the direction of the ship model 14. The cylindrical glass rod 13 is located at the tail of the ship model 14. The cylindrical glass rod 13 scatters the laser beam reflected by the reflector 12 into a surface laser. The CCD camera 11 is used to photograph the deck of the ship model.

[0028] like Figure 1 and 4 As shown, in the wind tunnel test of the present invention, the complete test mechanism also includes an optical plate 1, a small triangular fixing block 2, a support rod 5, a large triangular fixing block 6, a motor assembly and a pull rope. The optical plate 1 is detachably fixed to the outer surface of the upper wall plate of the wind tunnel, and the optical plate 1 can also be installed in other positions, such as above the ship model. The small triangular fixing block 2 and the large triangular fixing block 6 are relatively installed on the optical plate 1, the support rod 5 is horizontally installed on the large triangular fixing block 6, and the motor assembly is installed on the small triangular fixing block 2.

[0029] The pull rope is made of 304 stainless steel rope. There can also be two pull ropes; one end of one pull rope is fixed to the slot hole of the ear piece, and the other end passes through the pulley 4 and is fixed to the U-groove bearing 72; one end of the other pull rope is fixed to the slot hole of the other ear piece, and the other end passes through the pulley 4 and is fixed to the U-groove bearing 72. The pull rope passes through the wind tunnel from the top wind tunnel observation window.

[0030] The above-mentioned test system also includes a ship model base, ears and aviation floor. The ship model = the bottom is longitudinally or transversely placed with a bearing seat according to the selection of roll and pitch motion. For example, the ship model base includes a first seat bearing, a second seat bearing and a shaft. The shaft is used to pass through the bearing seats of the model and the floor to achieve single-degree-of-freedom motion of the ship model. The shaft is located on the central axis of the bottom of the ship model, and the shaft passes through the first seat bearing and the second seat bearing. There are two first seat bearings and two second seat bearings respectively. The two first seat bearings are installed at the bottom of the ship model, and the two second seat bearings are installed on the aviation floor, and the four bearings are kept at a certain distance. The ship model and the ship model base are combined together through the first seat bearing, and the ship model base is fixed to the aviation floor through the second seat bearing. The aviation floor is used to simulate the sea surface of the ship. Slots are provided on the ears.

[0031] The turnbuckle 3 is mounted on the large triangular fixed block 6, and the drawstring passes through the turnbuckle 3. The turnbuckle 3 is used to adjust the tightness of the drawstring.

[0032] A method for measuring using the above-mentioned measuring system comprises the following steps:

[0033] After connecting the pull rope, adjust the ship model to the neutral position, that is, ensure that the roll angle of the ship model is zero; adjust the U-slot bearing at the motor turntable to the farthest distance from the ship model, that is, ensure that the slot hole of the motor turntable and the center hole of the motor turntable are on the same vertical line; tighten the pull rope, and finally ensure that the pull ropes on both sides are taut and stressed, and the ship model and the motor turntable are in the neutral position at the same time.

[0034] When the stepper motor rotates clockwise, the rope on one side of the ship model is pulled up, and one side of the ship model begins to rise; after the motor turntable rotates 90° from the neutral position, the model rises to the maximum roll angle; when the stepper motor rotates to 180°, the model returns to the neutral position with a roll angle of 0°; the stepper motor continues to rotate from 180°, at this time the rope on the other side of the ship model is pulled up, and the other side of the model begins to rise, and reaches the maximum upward angle when the stepper motor turntable rotates to 270°, and when the turntable rotates back to the neutral position (360°), the model returns to the neutral state with a roll angle of 0°; the above is a motion cycle of the wind tunnel test ship attitude dynamic simulation system simulating roll motion;

[0035] In this embodiment, small magnets are installed at positions such as 0°, 90°, 180°, and 270° on the motor turntable. In the process of simulating the ship's posture, each time the motor turntable reaches the corresponding position, the small magnet approaches the Hall element, and the Hall element outputs a low-level signal to the synchronizer, which transmits it to the CCD camera and the laser transmitter, and the CCD camera takes a picture.

[0036] The above-mentioned laser transmitter generates a laser beam, changes the direction of the laser beam through a reflector, and then obtains a surface laser through a cylindrical glass rod to illuminate the cross section that needs to be photographed.

[0037] The present invention constructs a complete ship model dynamic deck flow field test system, uses reflectors and cylindrical glass rods to get rid of the position restriction of the wind tunnel space on the laser generation system in the particle image velocimetry system, and at the same time, based on the ship dynamic device, uses the law of the motor turntable, uses small magnets and Hall elements to achieve phase-locked shooting of multiple phases in the same period, saving limited wind tunnel test time.

[0038] Relevant wind tunnel tests have verified that the distributed small magnets in this embodiment have achieved the function of phase-locked photography of specific phases of multiple dynamic ships in one wind tunnel, and successfully used the separate special optical path to avoid the size limitation of the laser transmitter and the space limitation caused by the wind tunnel structure, such as Figure 6 As shown. The vorticity of the upwash vortex is weakened between -1° and 1°, and is enhanced between 1° and -2°. The reason is that when the ship is in a dynamic pitch-up state, it is equivalent to adding a vertical downward component velocity on the port side, which weakens the original pressure difference, so the vorticity of the upwash vortex is weakened; similarly, when the ship is in a dynamic pitch-down state, it is equivalent to adding a vertical upward component velocity on the port side, which enhances the original pressure difference, so the vorticity of the upwash vortex is enhanced. Therefore, it is proved that the present invention can achieve the goal of simply measuring the deck flow field of large dynamic ships in wind tunnel tests.

[0039] Based on the description of the preferred embodiments of the present invention, it should be clear that the present invention defined by the attached claims is not limited to the specific details set forth in the above description, and many obvious changes to the present invention that do not depart from the spirit or scope of the present invention may also achieve the purpose of the present invention.

Claims

1. A system for measuring the flow field on the deck of a large ship in a wind tunnel test, characterized in that: It includes a ship model, a motion control subsystem and a particle image velocimetry component; the motion control subsystem includes a motor component, the motor component includes a stepper motor, a U-slot bearing and a motor turntable, a center hole is provided at the center of the motor turntable to be installed on the rotating shaft of the stepper motor, and a slot is provided at a certain distance from the center hole to install the U-slot bearing; the particle image velocimetry component includes a Hall element, a small magnet, a laser emitter, a reflector, a cylindrical glass rod, a CCD camera, a synchronizer, and a particle image processing system; the small magnets are distributed on the same circumference inside the motor turntable, the Hall element is fixed on the stepper motor fixing frame, and the Hall element is directly opposite to the circumference where the small magnets are distributed; the CCD camera and the laser emitter are both connected to the synchronizer, the reflector is located on the light path emitted by the laser emitter, and the reflector reflects the laser to the direction of the ship model; the cylindrical glass rod is located at the tail of the ship model, and the cylindrical glass rod scatters the laser beam reflected by the reflector into a surface laser; the CCD camera is used to photograph the deck of the ship model.

2. The system for measuring the flow field on the surface of a large ship in a wind tunnel test according to claim 1, characterized in that: The small magnets are arranged according to the phases required for shooting, and when the motor turntable rotates, the small magnets face the Hall element within a certain period of time.

3. The system for measuring the flow field on the surface of a large ship in a wind tunnel test according to claim 1, characterized in that: The Hall element is a unipolar Hall element, which is used to output an electrical signal.

4. A method for measuring using the system according to any one of claims 1 to 3, comprising the following steps: After connecting the pull ropes on both sides of the ship model, adjust the ship model to a neutral position, that is, ensure that the roll angle of the ship model is zero; adjust the U-slot bearing at the motor turntable to the farthest distance from the ship model, that is, ensure that the slot hole of the motor turntable and the center hole of the motor turntable are on the same vertical line; tighten the pull ropes, and finally ensure that the pull ropes on both sides are in a taut state, and the ship model and the motor turntable are in a neutral position at the same time; When the stepper motor rotates clockwise, the rope on one side of the ship model is pulled up, and the ship model begins to rise; After the motor turntable rotates 90° from the neutral position, the ship model rises to the maximum roll angle; when the stepper motor rotates to 180°, the ship model returns to the neutral position with a roll angle of 0°; the stepper motor continues to rotate from 180°, at which time the rope on the other side of the ship model is pulled up, and the other side of the ship model begins to rise, and reaches the maximum upward angle when the stepper motor turntable rotates to 270°. When the turntable rotates back to the neutral position, the ship model returns to the neutral state with a roll angle of 0°; the above is a motion cycle of the wind tunnel test ship attitude dynamic simulation system simulating roll motion; In the process of simulating the ship's posture, every time the motor turntable reaches the corresponding position, the small magnet approaches the Hall element, and the Hall element outputs a low-level signal to the synchronizer, which transmits it to the CCD camera and laser transmitter, and the CCD camera takes a picture.

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